Name a stool concentration technique used in parasitology besides the Kato-Katz technique.

• A. Direct smear
• B. Formalin-ethyl acetate concentration technique (FECT)
• C. Gram stain
• D. ELISA for parasite antigens

Answer: (B)

Concentration of parasites in stool increases diagnostic sensitivity by pulling eggs, cysts, and larvae out of the debris and into a small, sediment-rich pellet that’s easier to inspect under the microscope. The formalin-ethyl acetate concentration technique achieves this by fixing the stool in formalin to preserve the parasites, then using ethyl acetate to dissolve fats and debris. After centrifugation, the sediment contains a higher density of parasite elements, so eggs, cysts, and larvae are more readily seen than in a direct smear. This method is flexible for detecting a variety of intestinal parasites and complements quantitative methods like Kato-Katz, which is primarily used for counting eggs to estimate intensity of infection rather than broadly increasing visual sensitivity. The other options aren’t concentration techniques: a direct smear offers only a quick, low-sensitivity look; Gram stain targets bacteria and is not routinely used for stool parasites; ELISA detects antigens or antibodies rather than concentrating stool material for microscopy.